Abstract-Broadband terahertz metamaterial absorber with two interlaced fishnet layers

AIP Advances

Siyu Tan, Fengping Yan,  Ningning Xu, Jingjing Zheng, Wei Wang, Weili Zhang,

Schematic of the proposed broadband metamaterial absorber: (a) the two interlaced square fishnet layers and the ground plane are separated by two identical polyimide spacers with the thickness h = 20 μm. (b) Microscopic graph of the fabricated sample. (c) and (d): The unit cell of the middle layer and the top layer with l = 150 μm, w1 = 35 μm and w2 = 15 μm.

https://aip.scitation.org/doi/10.1063/1.5017099

The realization of broadband absorption in the terahertz regime is of significant interest in high-sensitive signal detection and modulation. Previously, multi-layer metamaterials have been proposed and demonstrated to expand the absorption bandwidth by clustering multiple closely-positioned structures with different absorption peaks. Here, we proposed an alternative design for broadband metamaterial absorption by incorporating two interlaced fishnet layers, and achieved a broadband absorber with a full-width at half-maximum of about 0.99 THz. We also investigated the impact of the relative position of the two fishnet layers in the form of frequency tuning and expanding the absorption band.

Abstract-Ultrasensitive sensing with three-dimensional terahertz metamaterial absorber

Siyu Tan, Fengping Yan, Wei Wang, Hong Zhou, Yafei Hou,

http://iopscience.iop.org/article/10.1088/2040-8986/aab66e/pdf

Planar metasurfaces and metamaterial absorbers have shown great promise for label-free sensing applications at microwaves, optical and terahertz frequencies. The realization of high-quality-factor resonance in these structures is of significant interest to enhance the sensing sensitivities to detect the minute frequency shifts. We propose and demonstrate in this manuscript an ultrasensitive terahertz metamaterial absorber sensor based on three-dimensional split ring resonator absorber with a high quality factor of 60.09. The sensing performance of the proposed absorber sensor was systematically investigated through detailed numerical calculations and a maximum refractive index sensitivity of 34.40% RIU-1 was obtained. Furthermore, the absorber sensor can maintain a high sensitivity for a wide range of incidence angles up to 60° under TM polarization incidence. These findings would improve the design flexibility of the absorber sensors and further open up new avenues to achieve ultrasensitive sensing in terahertz regime.
© 2018 IOP Publishing Ltd

Abstract-Simultaneous measurement of refractive index and conductivity based on metamaterial absorber

Wei Wang1, Fengping Yan2.  Siyu Tan3, Luna Zhang4, Zhuoya Bai5, Dan Cheng6, Hong Zhou7 and Yafei Hou

http://iopscience.iop.org/article/10.1088/2040-8986/aa8fc1

An algorithm for the metamaterial sensors to simultaneously measure the refractive index and conductivity of the analyte is introduced. To verify the algorithm, a square ring metamaterial absorber is numerically calculated as a specific example in the terahertz frequency. Firstly, the sensing performances of the absorber on the refractive index (RI) and conductivity are evaluated separately. Then the relationship expressions between dual variables (frequency shift (FS) and amplitude modulation (AM)) and two arguments (RI and conductivity) can be obtained through mathematical fitting process. By reversely solving this equations set, the conductivity and RI of the analyte can be expressed as another equations set that can be solved easily. The proposed algorithm offers an effective method to determine RI and conductivity of the analyte by measuring the AM and FS of the reflection dip of the absorber sensor. To validate the effectiveness and accuracy of the algorithm, the FS and AM obtained from the simulations are plugged into the reverse equations set. Then the calculated n and σ are compared to their responding original values. The maximum percentage error between them are both less than 0.83%, which are small enough to illustrate the rightness of the proposed method.

Abstract-Terahertz metasurfaces with a high refractive index enhanced by the strong nearest neighbor coupling

Siyu Tan, Fengping Yan, Leena Singh, Wei Cao, Ningning Xu, Xiang Hu, Ranjan Singh, Mingwei Wang, and Weili Zhang
https://www.osapublishing.org/oe/abstract.cfm?URI=oe-23-22-29222

The realization of high refractive index is of significant interest in optical imaging with enhanced resolution. Strongly coupled subwavelength resonators were proposed and demonstrated at both optical and terahertz frequencies to enhance the refractive index due to large induced dipole moment in meta-atoms. Here, we report an alternative design for flexible free-standing terahertz metasurface in the strong coupling regime where we experimentally achieve a peak refractive index value of 14.36. We also investigate the impact of the nearest neighbor coupling in the form of frequency tuning and enhancement of the peak refractive index. We provide an analytical circuit model to explain the impact of geometrical parameters and coupling on the effective refractive index of the metasurface. The proposed meta-atom structure enables tailoring of the peak refractive index based on nearest neighbor coupling and this property offers tremendous design flexibility for transformation optics and other index-gradient devices at terahertz frequencies.

© 2015 Optical Society of America

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Abstract-Terahertz metasurfaces with a high refractive index enhanced by the strong nearest neighbor coupling

Siyu Tan, Fengping Yan, Leena Singh, Wei Cao, Ningning Xu, Xiang Hu, Ranjan Singh, Mingwei Wang, and Weili Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-23-22-29222

The realization of high refractive index is of significant interest in optical imaging with enhanced resolution. Strongly coupled subwavelength resonators were proposed and demonstrated at both optical and terahertz frequencies to enhance the refractive index due to large induced dipole moment in meta-atoms. Here, we report an alternative design for flexible free-standing terahertz metasurface in the strong coupling regime where we experimentally achieve a peak refractive index value of 14.36. We also investigate the impact of the nearest neighbor coupling in the form of frequency tuning and enhancement of the peak refractive index. We provide an analytical circuit model to explain the impact of geometrical parameters and coupling on the effective refractive index of the metasurface. The proposed meta-atom structure enables tailoring of the peak refractive index based on nearest neighbor coupling and this property offers tremendous design flexibility for transformation optics and other index-gradient devices at terahertz frequencies.

© 2015 Optical Society of America

Full Article  |  PDF Article

Abstract-Broadband Terahertz Transparency in a Switchable Metasurface

Xiaoqiang Su 
Key Lab. of Optoelectron. Inf. & Technol., Tianjin Univ., Tianjin, China 
Chunmei Ouyang ; Ningning Xu ; Siyu Tan ; Jianqiang Gu ; Zhen Tian ; Jiaguang Han ; Fengping Yan ; Weili Zhang

http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?reload=true&arnumber=7008493&punumber%3D4563994

Plasmon-induced transparency in terahertz metamaterials markedly modifies the dispersive properties of an otherwise opaque medium and reveals unprecedented prospects on novel functional components. However, plasmon-induced transparency in metamaterials so far exists in a narrow frequency band or without actively tunable abilities. Here, we demonstrate optical control of a broadband plasmon-induced transparency in a hybrid metamaterial made from integrated silicon-metal unit cells. Attributed to the modification in damping rate of the dark mode resonators under optical excitation, a giant dynamic amplitude modulation of the broadband transparency window is observed. The scheme suggested here is promising in developing broadband active slow-light devices and realizing on-to-off switching responses of the terahertz radiation at room temperature.

(a) Schematic diagram of the active broadband PIT metamaterial. The geometrical parameters are: $l = 86 muhbox{m}$, $a = 28 muhbox{m}$, $b = 48 muhbox{m}$, $w = 4 muhbox{m}$, $D_{rm x}= 26 muhbox{m}$, $D_{rm y}= 10 muhbox{m}$, $P_{rm x}= 114 muhbox{m}$, and $P_{rm y}= 134 muhbox{m} $. The bottom right of panel (a) is a microscopic image of the fabricated metamaterial. (b) Experimental diagram of the optical pump-terahertz probe measurement.

Published in:

Photonics Journal, IEEE  (Volume:7 ,  Issue: 1 )

Article#:

5900108

ISSN :

1943-0655

INSPEC Accession Number:

14880065

DOI:

10.1109/JPHOT.2015.2390146

Date of Publication :

13 January 2015

Date of Current Version :

30 January 2015

Issue Date :

Feb. 2015

Sponsored by :

IEEE Photonics Society

Publisher:

IEEE